U.S. patent number 9,375,972 [Application Number 14/380,951] was granted by the patent office on 2016-06-28 for writing instrument.
This patent grant is currently assigned to KABUSHIKI KAISHA PILOT CORPORATION. The grantee listed for this patent is KABUSHIKI KAISHA PILOT CORPORATION. Invention is credited to Hirotaka Masuda, Naoto Masushige.
United States Patent |
9,375,972 |
Masuda , et al. |
June 28, 2016 |
Writing instrument
Abstract
A writing instrument includes a pen point retaining member, a
pen point that is attached to a first end of the pen point
retaining member, an ink tank that is attached to a second end of
the pen point retaining member, and an ink that is accommodated in
the ink tank. The ink includes a lubricating interface
layer-forming compound, and a carbonaceous film is formed on at
least one of a surface of the ball or a contact portion of the ball
holding portion with the ball.
Inventors: |
Masuda; Hirotaka (Kanagawa-ken,
JP), Masushige; Naoto (Aichi-ken, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA PILOT CORPORATION |
Tokyo-to |
N/A |
JP |
|
|
Assignee: |
KABUSHIKI KAISHA PILOT
CORPORATION (Tokyo-To, JP)
|
Family
ID: |
49082378 |
Appl.
No.: |
14/380,951 |
Filed: |
February 19, 2013 |
PCT
Filed: |
February 19, 2013 |
PCT No.: |
PCT/JP2013/053953 |
371(c)(1),(2),(4) Date: |
August 26, 2014 |
PCT
Pub. No.: |
WO2013/129178 |
PCT
Pub. Date: |
September 06, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20150298488 A1 |
Oct 22, 2015 |
|
Foreign Application Priority Data
|
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|
|
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Feb 27, 2012 [JP] |
|
|
2012-040346 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B43K
7/06 (20130101); C09D 11/18 (20130101); B43K
1/084 (20130101); B43K 7/02 (20130101); C22C
29/08 (20130101); B43K 1/08 (20130101); B43K
7/005 (20130101); C23C 16/56 (20130101); B43K
7/105 (20130101); C23C 16/0272 (20130101); B43K
7/00 (20130101); B43K 7/10 (20130101); C23C
16/26 (20130101); B43K 1/082 (20130101) |
Current International
Class: |
B43K
5/16 (20060101); C23C 16/26 (20060101); C23C
16/56 (20060101); C09D 11/18 (20060101); B43K
7/10 (20060101); C23C 16/02 (20060101); C22C
29/08 (20060101); B43K 7/00 (20060101); B43K
1/08 (20060101); B43K 29/00 (20060101); B43K
7/02 (20060101); B43K 7/06 (20060101) |
Field of
Search: |
;401/216,208-215 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
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2001-121868 |
|
May 2001 |
|
JP |
|
2001121868 |
|
May 2001 |
|
JP |
|
2002-505716 |
|
Feb 2002 |
|
JP |
|
2003-196819 |
|
Jul 2003 |
|
JP |
|
2004-338134 |
|
Dec 2004 |
|
JP |
|
2004338134 |
|
Dec 2004 |
|
JP |
|
2005-324336 |
|
Nov 2005 |
|
JP |
|
2010-240931 |
|
Oct 2010 |
|
JP |
|
2012-12329 |
|
Jan 2012 |
|
JP |
|
2012-56198 |
|
Mar 2012 |
|
JP |
|
Other References
Supplementary European Search Report dated Sep. 25, 2015 issued in
corresponding European Patent Application No. 13754103.3. cited by
applicant .
English translation of International Preliminary Report on
Patentability issued Sep. 12, 2014 in International (PCT)
Application No. PCT/JP2013/053953. cited by applicant .
International Search Report (ISR) issued May 21, 2013 in
International (PCT) Application No. PCT/JP2013/053953. cited by
applicant.
|
Primary Examiner: Laurenzi; Mark A
Assistant Examiner: Abebe; Thomas M
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A writing instrument comprising: a pen point retaining member; a
pen point that comprises a ball and a ball holding portion that
rotatably holds the ball, and is attached to a first end of the pen
point retaining member; an ink tank that is releasably attached to
a second end of the pen point retaining member; and an ink that is
accommodated in the ink tank and comprises a lubricating interface
layer-forming compound, wherein a carbonaceous film is formed on at
least one of a surface of the ball or a contact portion of the ball
holding portion with the ball, the carbonaceous film comprising a
carbon atom and an oxygen atom bound to the carbon atom, and
wherein surface tension of the ink is between 20 mN/m and 40 mN/m
in an environment at 20.degree. C.
2. The writing instrument according to claim 1, wherein the
carbonaceous film is formed on both of the surface of the ball and
the contact portion of the ball holding portion with the ball.
3. The writing instrument according to claim 1, wherein the ball is
selected from the group consisting of metals, ceramics, and alloys
thereof.
4. The writing instrument according to claim 1, wherein a
proportion of an sp.sup.3 carbon-carbon bond to an sp.sup.2
carbon-carbon bond, contained in the carbonaceous film, is 0.3 or
more.
5. The writing instrument according to claim 4, wherein a rate of a
bond containing oxygen to the total bond of carbon contained in the
carbonaceous film is 0.1 or more and 0.5 or less.
6. The ball-point pen according to claim 1, wherein the
carbonaceous film is formed on the surface of the ball or the
contact portion of the ball holding portion with the ball via an
intermediate layer, and the intermediate layer comprises carbon and
silicon.
7. The writing instrument according to claim 1, wherein the
lubricating interface layer-forming compound is an organic compound
comprising an organic acid group or an organic acid residue.
8. The writing instrument according to claim 7, wherein the organic
acid group is carboxyl group.
9. The writing instrument according to claim 1, wherein the pen
point is unreleasably attached to the pen point retaining member.
Description
TECHNICAL FIELD
The present invention relates to writing instruments. Specifically,
the present invention relates to a writing instrument including a
pen point retaining member, a pen point that is attached to a first
end of the pen point retaining member, an ink tank that is attached
to a second end of the pen point retaining member, and an ink that
is accommodated in the ink tank.
BACKGROUND ART
There has been conventionally known a ball-point pen, in which an
ink tank in which an ink for a ball-point pen is accommodated is
disposed in a shaft cylinder, and a ball is put on the bottom wall
of a ball holding portion, and which includes a pen point of which
the leading end portion is inwardly crimped, whereby a part of the
ball is allowed to protrude from the leading edge of the pen point,
and the ball is rotatably held.
A ball-point pen performs writing by transferring ink, flowing out
of an ink tank, onto a body to be recorded, such as paper, or by
allowing the ink to infiltrate into the body to be recorded, due to
rotation of a ball. The wear of the ball and the inner surface of a
ball holding portion prevents the ball from smoothly rotating,
results in great deterioration of writing characteristics, and
finally precludes writing. Therefore, the reduction of the wear of
the ball and the ball holding portion is an important problem.
Use of a ceramic ball, coating of the surface of a metallic ball
with a rigid material such as a diamond-like carbon film for
reducing the wear of the ball and the ball holding portion (for
example, Patent Literature 1), and the like have been attempted
with respect to such problems. Coating of the surface of not only
the ball but also the ball holding portion with a rigid material
for reducing the wear of the ball holding portion by the ball has
been also attempted.
CITATION LIST
Patent Literature
Patent Literature 1: Japanese Patent Laid-Open No. 2004-338134
SUMMARY OF INVENTION
Technical Problem
However, even when only the hardness of a ball or a ball holding
portion is increased as in Patent Literature 1, it is difficult to
prevent the ball and the ball holding portion from being worn to
realize sufficient durability. This is because when the contact
site between the ball and the ball holding portion is
microscopically observed, the contact site may be in the state of
boundary lubrication in which the ball and the ball holding portion
come into direct contact with each other without the existence of
an ink for a writing instrument in the interface between the ball
and the ball holding portion. Such a phenomenon has tended to be
prone to occur particularly when an ink having low viscosity has
been used.
A state in which an appropriate amount of ink is present on the
interface between the ball and the ball holding portion, and the
ball and the ball holding portion do not come into direct contact
with each other is important for reducing such wear of the ball and
the ball holding portion.
Solution to Problem
The writing instrument according to the present invention is a
writing instrument including:
a pen point retaining member;
a pen point that includes a ball and a ball holding portion that
rotatably holds the ball, and is attached to a first end of the pen
point retaining member;
an ink tank that is attached to a second end of the pen point
retaining member; and
an ink for a writing instrument that is accommodated in the ink
tank and includes a lubricating interface layer-forming
compound,
wherein a carbonaceous film is formed on at least one of a surface
of the ball or a contact portion of the ball holding portion with
the ball; and the carbonaceous film includes a carbon atom and an
oxygen atom bound to the carbon atom.
Advantageous Effects of Invention
The present invention is to provide a ball-point pen in which
favorable writing can be obtained over a long distance and a long
term.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a longitudinal cross-sectional view of a writing
instrument according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the line A-A of FIG. 1.
FIG. 3 is an enlarged vertical longitudinal sectional view of the
principal portion of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
An embodiment of the writing instrument according to the present
invention will be explained in detail below with reference to the
drawings.
The cross-sectional view of the writing instrument according to one
embodiment of the present invention is as illustrated in FIG. 1.
The writing instrument 1 is a direct liquid type writing
instrument, in which a pen point 2 and an ink tank 4 are attached
to both ends of a pen point retaining member 3. On the pen point
retaining member 3, combs 31 in which an ink effused due to the
increase of the internal pressure of the ink tank 4 is temporarily
retained are formed. Reservation grooves 32 and a guiding groove 33
are defined by the combs 31, so that the function of reserving an
ink is exerted. The ink tank 4 is attached to a rear end side when
the pen point side of the writing instrument 1 is regarded as a
leading end side. In FIG. 1, the ink tank 4 is releasably attached
without limitation. However, in the present invention, since the
durability of a pen point portion is very high, the pen point
portion can be used for a long term, and it is preferable that ink
can be refilled. Therefore, the writing instrument according to the
present invention is a writing instrument with an interchangeable
ink tank.
The writing instrument 1 illustrated in FIG. 1 further includes a
leading shaft 5 and a rear shaft 6. The leading shaft 5
accommodates the pen point retaining member 3, and a threaded
engagement structure for releasably attaching the rear shaft 6 is
disposed in the rear end portion thereof. A structure to which the
ink tank 4 is releasably attached is disposed in the rear end side
of the pen point retaining member accommodated in the leading shaft
5. In the writing instrument illustrated in FIG. 1, the rear end of
the leading shaft 5 described below protrudes to form a cylindrical
binding portion 52, to which the ink tank 4 is releasably
connected. The ink tank 4 is accommodated in the rear shaft 6 by
attaching the rear shaft 6. The pen point 2 is attached to the
leading end of the pen point retaining member 3 via a holder 7. An
ink is guided from the ink tank 4 to the pen point 2 by an ink
guiding member 8 which penetrates the pen point retaining member
3.
Leading Shaft
The leading shaft 5 includes a cylindrical structure, of which both
ends are opened, for example, a hollow cylinder, and is obtained by
injection molding or the like of a synthetic resin (for example,
polypropylene, polycarbonate, or the like). The rear end portion of
the leading shaft 5 is provided with a cylindrical threaded
engagement portion 51, of which the diameter is reduced, and the
cylindrical binding portion 52 which is concentrically placed on
the inside of the threaded engagement portion 51. A male screw
portion 51a is formed on the outer surface of the threaded
engagement portion 51. The binding portion 52 is pressed into the
opening of the ink tank 4 when the ink tank 4 is attached.
Furthermore, a projection 52a for backward pushing off a plug body
41 in the opening of the ink tank 4 to open the plug when the ink
tank 4 is attached is formed in a part of the rear end of the
binding portion 52.
Rear Shaft
The rear shaft 6 includes a bottomed cylindrical body, of which the
leading end side is opened, and is obtained by injection molding or
the like of a synthetic resin (for example, polypropylene,
polycarbonate, or the like). A female screw portion 61 that can be
threadedly engaged releasably with the male screw portion 51a of
the threaded engagement portion 51 of the leading shaft 5 is formed
on the inner peripheral surface of the leading end side opening of
the rear shaft 6. Further, the rear shaft 6 preferably has
transparency so that the amount of residual ink in the ink tank 4
can be viewed from the outside.
Pen Point Retaining Member
The pen point retaining member 3 is obtained by injection molding
or the like of a synthetic resin (for example, ABS resin or the
like). The pen point 2 and the ink tank 4 are attached to the pen
point retaining member 3. In FIG. 1, the ink tank 4 is releasably
attached while the pen point 2 is unreleasably attached. In other
words, in the present invention, since the wear of the pen point is
reduced by the combination of the specific pen point and the
specific ink, there is no need for exchanging the pen point, and
therefore, it is not necessary to allow the pen point to be
releasable. However, the pen point can also be releasably attached
to be intended to be used for a longer term.
In the present invention, the pen point retaining member 3 has the
function of linking the ink tank to the pen point. In order to
realize a higher writing property, the pen point retaining member
is preferably provided with an ink reserving function. The writing
instrument illustrated in FIG. 1 includes the pen point retaining
member having the ink reserving function.
The pen point retaining member 3 includes the plural combs 31 which
are discoidal. The reservation grooves 32 for temporarily reserving
an ink are formed mutually between the combs 31. The slit-like
guiding groove 33 that is connected to each reservation groove 32
and extends in an axial direction is formed on the combs 31. A
communication groove 35 which is connected to the guiding groove 33
and of which the side closer to the ink tank 4 is opened is
installed to penetrate back and forth a collar portion 34 located
at the rearmost end of the group of the combs 31 of the pen point
retaining member 3 (see FIG. 2). Further, concave grooves 36 for
circulating air are formed on the combs 31. Further, a central hole
37 is installed to penetrate the center of the pen point retaining
member 3. A first ink guiding member 81 including an
extrusion-molded body of a synthetic resin is attached by being
inserted into the central hole 37.
The member having the ink reserving function of temporarily
retaining an ink effused due to the increase of the internal
pressure of the ink tank was described as an example of the pen
point retaining member, but the pen point retaining member is not
particularly limited thereto.
Ink Tank
In the writing instrument illustrated in FIG. 1, the ink tank 4 is
obtained by injection-molding or the like of a synthetic resin (for
example, polyethylene or the like). The ink tank 4 is generally a
bottomed cylindrical body of which the leading end is opened and
the rear end is closed, and in which the inner peripheral surface
of the opening is provided with the plug body 41, which blockades
the interior of the ink tank 4, by fitting, welding, adhering, or
the like. An ink for a writing instrument is accommodated directly
in the ink tank 4. The ink tank 4 preferably has transparency so
that the amount of residual ink therein can be viewed. The ink tank
that is a bottomed cylindrical body is illustrated in FIG. 1, but
the ink tank is not limited thereto. In other words, the ink tank
may be an ink accommodating tube of which a terminal portion is
opened.
Although the direct liquid type writing instrument in which ink is
accommodated directly in the ink tank is described as an example in
FIG. 1, an inner cotton type writing instrument in which inner
cotton is impregnated with ink is also acceptable.
Further, examples of the ink used in the writing instrument
according to the present invention include water-based inks,
water-based gel inks, oil-based inks, and the like, without
particular limitation. However, a water-based ink with Newtonian
viscosity and a water-based ink imparted with shear-thinning
viscosity are preferred since the contact portion between the ball
and the ball holding portion tends to become in boundary
lubrication to be prone to be worn, and therefore, the effect of
improvement in durability by the present invention is prominently
produced. Furthermore, the viscosity of the ink used in the present
invention is not also particularly limited, but the case of using
an ink having a viscosity of less than 10 mPas (20.degree. C.) in
writing is also preferred since the effect of the present invention
is similarly prominently produced.
Further, the ink used in the writing instrument according to the
present invention includes a lubricating interface layer-forming
compound. As used herein, the lubricating interface layer-forming
compound is a compound having the action of forming a lubricating
interface layer between the ball and the inner surface of the ball
holding portion. This lubricating interface layer is a layer having
the action of inhibiting the ball and the ball holding portion from
coming into direct contact with each other and from being in
boundary lubrication.
The lubricating interface layer-forming compound is not
particularly limited if enabling the formation of a lubricating
interface layer between the ball and the ball holding portion as
described above, and specific examples thereof include an organic
compound having an organic acid group or an organic acid
residue.
In the present invention, the organic acid group is an organic
acidic group such as, for example, carboxyl group (--COOH),
phosphoryl group (--P(.dbd.O)(OH).sub.2), sulfo group
(--SO.sub.3H), sulfino group (--SO.sub.2H), or hydroxyphenyl group
(--C.sub.6H.sub.4OH). Of these, carboxyl group or phosphoryl group
is preferred, and carboxyl group is particularly preferred. These
groups exert superior wear prevention effects, and this is
considered to be because these groups have particularly high
affinities for a carbonaceous film (detailed below). Further, the
organic acid residues are groups obtained by removing hydrogen from
the organic acid groups, such as, for example, --COO--,
--P(.dbd.O)(OH)O--, --P(.dbd.O)(O--).sub.2, --SO.sub.3--,
--SO.sub.2--, and --C.sub.6H.sub.4O--. The organic acid residues
are formed by reaction of the organic acid groups with other metal
atoms or organic compounds such as alcohols. The lubricating
interface layer-forming compound in the present invention may
contain two or more groups of, or two or more kinds of the organic
acid groups or the organic acid residues.
Further, an organic group bound to the organic acid group or the
organic acid residue can be appropriately selected depending on an
ink of interest and is not particularly limited. Such an organic
group is generally a saturated or unsaturated hydrocarbon group,
and for example, a lubricating interface layer-forming compound
used in a water-based ink preferably has a substituent that
enhancing water solubility because of desirably having high water
solubility. Such substituents include hydroxyl group, ether group,
carbonyl group, ketone group, amino group, amide group, alkyleneoxy
group, acyl group, carboxyl group, ester group, phosphate group,
sulfonate group, and the like. In other words, the organic acid
group may also exert the function of enhancing water
solubility.
Such lubricating interface layer-forming compounds include fatty
acids, alkylbenzene sulfonic acids, phosphate esters, amino acids,
N-acylamino acids, aliphatic amide alkylene oxide adducts,
terpenoid acid derivatives, salts thereof, and the like. More
specifically, preferred lubricating interface layer-forming
compounds include oleic acid, stearic acid, linolic acid, linolenic
acid, ricinoleic acid, dodecylbenzenesulfonic acid, polyoxyethylene
alkyl ether phosphate ester, polyoxyethylene alkyl phenyl ether
phosphate ester, alanine, glycine, lysine, threonine, serine,
proline, sarcosine, N-acylsarcosine, polyoxyethylene fatty acid
amide, salts thereof, and the like. These may also be used in
combination of two or more kinds.
In the present invention, the lubricating interface layer-forming
compound is considered to have the action of enhancing an affinity
between the ink and the carbonaceous film. For example, there has
been an ink used in a conventional ball-point pen, containing water
and a component having a hydrophilic functional group, such as
alcohol or glycol ether. The ink containing such a component has
had a low affinity for a conventionally used ball, for example, a
ball comprising silicon carbide, not subjected to surface
treatment, and a contact portion between a ball and a ball holding
portion has tended to be prone to be in boundary lubrication.
However, in the present invention, the carbonaceous film having a
carbon-oxygen bond is formed on either ball or ball holding
portion, and it is easy to offer fluid lubrication between the ball
and the ball holding portion by using an ink having a high affinity
therefor. Therefore, the ink containing the lubricating interface
layer-forming compound having a high affinity for the carbonaceous
film having a carbon-oxygen bond is used to form the lubricating
interface layer between the ball and the ball holding portion and
to make it possible to enhance the effect of inhibiting the wear of
the ball and the like. The reason why the lubricating interface
layer is formed in such a manner is considered to be that when an
uncombined hand of carbon exists on the surface of the carbonaceous
film, the uncombined hand and the lubricating interface
layer-forming compound are bound by a reaction such as chemical
adsorption by the rotation of the ball, and the surface of the
carbonaceous film is coated with the lubricating interface
layer-forming compound to form a layer.
When the ink for a writing instrument is a water-based ink for a
ball-point pen, the ink preferably has a pH of 7 to 13, more
preferably a pH of 7 to 9. The ink is allowed to be alkaline or
weak alkaline in such a manner, to obtain the dissolution stability
of the lubricating interface layer-forming compound in the
water-based ink for a ball-point pen and to further improve the
temporal stability of the lubricating interface layer due to the
adsorption of the functional group of the lubricating interface
layer-forming compound on the surface of the carbonaceous film.
When the carbonaceous film is formed only on either ball or ball
holding portion, a part that is not coated with the carbonaceous
film is exposed. When the ink comes into contact with the exposed
part, a metal component contained in the ball or the ball holding
portion, for example, a metallic binding material used in the ball
may be eluted with time. The eluted metal component is oxidized,
becomes insoluble in the ink, and may adhere to the ball surface
and the like. The elution and the adhesion may result in a defect
such as the deterioration of surface smoothness, the inhibition of
the rotation of the ball, and the heavier feeling of writing; the
inhibition of the smooth outflow of the ink and patchy handwriting;
or the like. In view of such facts, in consideration of the
temporal stability of a ball-point pen, a pH adjuster such as a
basic compound represented by an amine can be added particularly
when a water-based ink for a ball-point pen is used. In this case,
the adsorption of the lubricating interface layer-forming compound,
which is generally acidic, to the surface of the carbonaceous film
tends to be inhibited; however, since the deterioration of writing
performance due to the elution of a metal component after a lapse
of time can be suppressed, the temporal stability of the writing
instrument may be able to be comprehensively improved.
Pen Point
The pen point 2 has a structure in which a ball 24 is rotatably
held in the ball holding portion disposed in the leading end. Such
a structure is also referred to as a ball-point pen tip. In the
ball holding portion, the ball 24 is rotatably held by an inward
leading edge 22 formed by radially inwardly press-deforming the
taper-like leading end portion of a metallic pipe 21 (for example,
a pipe comprising stainless steel, copper, aluminum, nickel, or the
like), and by a plurality of (for example, three or four) inwardly
projecting portions 23 formed by radially inwardly press-deforming
a side wall in the vicinity of the leading end of the pipe. The
plural inwardly projecting portions 23 are placed generally at an
equal spacing circumferentially on the inner surface of the pipe 2.
The ball is held by the extremely leading end portion 22 and the
inwardly projecting portions 23 so as not to be removed from the
pen point. The swaging angle of the leading edge 22 is generally
allowed to be from 50.degree. to 100.degree. in consideration of an
angle with respect to paper and an ink flow path.
Although the pipe-type ball-point pen tip formed by
press-processing or the like of a pipe made of stainless steel is
illustrated as an example in FIG. 1, a cutting-type ball-point pen
tip formed by cutting and processing a stainless steel wire rod
with a drill is also acceptable. Examples of the material of the
ball 24 include sintered bodies of tungsten carbide, ceramics of
zirconia, alumina, silica, silicon carbide, and the like, stainless
steel described as examples, or the like.
As the material of the ball held by the pen point, which is not
particularly limited, a material comprising a metal or a ceramic is
generally used. Since durability is demanded in the writing
instrument according to the present invention, it is preferable to
select a material having a high hardness. For example, a ceramic
such as tungsten carbide, zirconium oxide, aluminum oxide, silicon
oxide, or silicon carbide, or a metal such as stainless steel is
used. A cemented carbide alloy comprising a ceramic and a metallic
binding material may also be used. As such a cemented carbide
alloy, an alloy comprising tungsten carbide and a metallic binding
material such as cobalt or nickel is known.
In the writing instrument illustrated in FIG. 1, the ball of
tungsten carbide (equivalent to ISO K-10) having a diameter of 0.5
mm is used. The size of the ball is determined by the application
of the writing instrument, the width of a drawn line demanded in
writing, or the like, and is generally selected from the range of
0.25 to 2.0 mm. In the present invention, a more preferred effect
can be exerted when the ball having a small diameter, for example,
the small-diameter ball having a diameter of 0.5 mm or less is
used. This is because in the case of writing of the same distance,
the lower diameter of the ball results in the more rotation number
of the ball and therefore in a tendency to more easily wear the
ball holding portion.
Further, the clearance between the ball and the inner surface of
the ball holding portion in the pen point greatly influences a
writing property. Therefore, it is preferable to suitably adjust
the clearance. The suitable clearance varies according to the
viscosity of an ink for a writing instrument used, or the like. For
example, in a case in which the ink for a writing instrument has a
viscosity of less than 10 mPas, a sufficient consumption of ink is
not obtained and there is the fear of patchy writing or the like
when the clearance at a writing distance of 0 m (no use of the
writing instrument) is too narrow, while there is the fear of
dripping of the ink when the clearance is too wide. Therefore, the
clearance is preferably 5 .mu.m or more and 25 .mu.m or less, more
preferably 10 .mu.m or more and 20 .mu.m or less, most preferably
15 .mu.m or more and 18 .mu.m or less.
Carbonaceous Film
In the writing instrument according to the present invention, a
carbonaceous film is formed on at least one of the surface of the
ball or the contact portion of the ball holding portion with the
ball. The carbonaceous film may be formed on both of the surface of
the ball and the contact portion. In FIG. 3, an example in which a
carbonaceous film 24C is formed on the surface of a ball body 24A
via an intermediate layer 24B (detailed below) is illustrated. In
the present invention, a material including the ball body 24A as
well as the intermediate layer 24B and the carbonaceous film 24C
may be referred to as the ball 24. When the carbonaceous film is
formed on the ball holding portion, the carbonaceous film may be
formed only on a part coming into contact with the ball, while the
carbonaceous film may also be formed in a wider range than the
actual contact part from the viewpoint of the easiness of
production, deformation due to use, and the like. Furthermore, the
carbonaceous film may be formed on the whole inner surfaces of the
ball holding portion.
In the present invention, the carbonaceous film has a carbon atom
and an oxygen atom bound to the carbon atom. Therefore, the
durability of the ball or the ball holding portion is increased. In
addition, since the carbonaceous film in the present invention has
a high affinity for an ink, the ink is held in a gap between the
ball and the interior of the ball holding portion, and direct
contact between the ball and the ball holding portion is inhibited.
As a result, the wearing of the ball and the interior of the ball
holding portion due to the direct contact between the ball and the
ball holding portion can be reduced, and the durability is further
improved. In addition, since the deterioration of the feeling of
writing due to use is inhibited by the improvement in durability,
the need for exchanging the pen point is substantially eliminated,
and a ball-point pen in which stable writing performance is
satisfied for a long term can be realized. Further, when the
carbonaceous film is formed on the ball surface, an affinity
between the ball surface and ink is improved to thereby enable the
stabilization of the supply of the ink to a contact portion between
the ball and a paper surface during writing, therefore, more
uniform handwriting and the favorable feeling of writing can be
realized, and a writing property can be allowed to be
favorable.
In the carbonaceous film, a carbon atom is bound to an oxygen atom
in various forms. Specifically, a carbon atom and an oxygen atom
are considered to be bound to each other in the forms of C--O,
O.dbd.C--O, and C.dbd.O. It is considered that C--O mainly
constitutes hydroxyl group, ethers, and the like, C.dbd.O mainly
constitutes carbonyl group, ketones, and the like, and O.dbd.C--O
mainly constitutes carboxyl group, esters, and the like in general.
These bonds are considered to enhance an affinity for an ink. In
addition, a carbon atom is bound to carbon or hydrogen in the form
of C--C or C--H. Accordingly, the affinity between the carbonaceous
film and the ink on the surface of the carbonaceous film is
enhanced with increasing the rate (hereinafter referred to as
CO.sub.total) of bonds containing oxygen (C--O, O.dbd.C--O, and
C.dbd.O) to all the bonds of carbon (C--O, O.dbd.C--O, C.dbd.O,
C--C, and C--H). A value of CO.sub.total is preferably 0.1 or more
and more preferably 0.15 or more since the affinity between the
carbonaceous film and the ink is increased, and it is easy to
maintain stable writing performance for a long term and over a long
distance. In contrast, since the excessively high value of
CO.sub.total tends to result in reduced bonds between carbon atoms
and in decreased hardness, the value is preferably 0.5 or less and
more preferably 0.45 or less.
In the present invention, the carbonaceous film can be formed on
the ball surface or the contact portion of the ball holding portion
with the ball by an optional method. The carbonaceous film may be
formed on either or both of the ball surface or the ball holding
portion. However, since the formation of the carbonaceous film on
the ball surface results in the reduction of wear between the ball
and the ball holding portion and in the stabilization of the supply
of ink as described above, it is preferable to form the
carbonaceous film on at least the ball surface.
A method of forming the carbonaceous film is not particularly
limited. For example, the formation can be performed by a plasma
chemical vapor phase deposition method (plasma CVD method), a
catalytic chemical vapor phase deposition method (CAT-CVD method),
or the like using hydrocarbon gas as a raw material. The formation
can also be performed by a sputtering method, an arc ion plating
method, or the like with solid graphite as a raw material.
Furthermore, the formation may be performed by another method or by
a combination of a plurality of methods.
The carbonaceous film used in the present invention is a film
containing an sp.sup.2 carbon-carbon bond (graphite bond) and an
sp.sup.3 carbon-carbon bond (diamond bond), which film is
represented by a diamond like film (DLC film). A film in an
amorphous state, such as a DLC film, or a film in a crystalline
state, such as a diamond film, is acceptable. However, in the
carbonaceous film in the present invention, a higher proportion of
an sp.sup.3 carbon-carbon bond to an sp.sup.2 carbon-carbon bond is
preferred since the hardness of the carbonaceous film is higher.
Specifically, the proportion of the sp.sup.3 carbon-carbon bond to
the sp.sup.2 carbon-carbon bond is preferably 0.3 or more. Further,
it is presumed that when much sp.sup.3 carbon exists in the
carbonaceous film, the number of uncombined hands that exist in the
surface of the carbonaceous film is relatively increased, the
amount of lubricating interface layer-forming compound that reacts
with the combined hands is thus increased, and a sufficient
lubricating interface layer is formed.
Further, although the carbonaceous film typically contains an
sp.sup.2 carbon-hydrogen bond and an sp.sup.3 carbon-hydrogen bond,
a carbon-hydrogen bond is not an essential component in the
carbonaceous film in the present invention. To the carbonaceous
film, silicon (Si), fluorine (F), or the like may also be added in
a range in which the effect of the present invention is not
deteriorated.
Further, a method of introducing a carbon-oxygen bond into the
carbonaceous film may be performed by irradiation with, for
example, oxygen plasma, plasma of a gas containing oxygen, or the
like. As the gas containing oxygen, water vapor, air, or the like
can be used. A gas of an organic substance compound containing an
oxygen atom, or the like can also be used. Furthermore, oxygen can
also be introduced by irradiating the carbonaceous film with
ultraviolet rays in an atmosphere containing oxygen or by immersing
the carbonaceous film in an oxidative solution. When the
carbonaceous film is formed, a carbon-oxygen bond can also be
introduced by increasing the concentration of oxygen in an
atmosphere when the carbonaceous film is formed. Just after the
formation of the carbonaceous film, an uncombined hand exists on
the surface thereof. Therefore, the uncombined hand can also be
allowed to react with oxygen to introduce a carbon-oxygen bond by
leaving the carbonaceous film, just after having been formed,
standing in an atmosphere containing oxygen. A carbon atom with an
uncombined hand may also exist if a carbon-oxygen bond is
introduced.
The film thickness of the carbonaceous film is not particularly
limited but preferably ranges from 0.001 .mu.m to 3 .mu.m, more
preferably ranges from 0.005 .mu.m to 1 .mu.m. Further, the
carbonaceous film can be formed directly on the surface of the ball
or the ball holding portion; however, in order to allow the ball or
the ball holding portion and the carbonaceous film to more firmly
adhere to each other, it is preferable to dispose an intermediate
layer. As the material of the intermediate layer, various materials
can be used depending on the kind of the ball or the ball holding
portion, and, for example, a known material such as an amorphous
film comprising silicon (Si) and carbon (C), titanium (Ti) and
carbon (C), or chromium (Cr) and carbon (C) can be used. The
thickness thereof is not particularly limited but preferably ranges
from 0.001 .mu.m to 0.3 .mu.m and more preferably ranges from 0.005
.mu.m to 0.1 .mu.m. The intermediate layer can be formed by using,
for example, a sputtering method, a CVD method, a plasma CVD
method, a spraying method, an ion plating method, an arc ion
plating method, or the like.
The pen point 2 is attached to the front of the holder 7. In
addition, the rear of the holder 7 is pressed into the leading end
opening of the central hole 37 of the ink retaining member 3. In
other words, the pen point 2 is attached to the ink retaining
member 3 via the holder 7. The holder 7 includes a collar-like
front, to which the pen point 2 is attached, and a rear pressed
into the leading end opening of the central hole 37 of the ink
retaining member 3. The holder 7 is obtained by injection-molding
or the like of a synthetic resin or the like.
The ink guiding member 8 includes the first ink guiding member 81,
a second ink guiding member 82, and a third ink guiding member 83.
The second ink guiding member 82 including a fiber-processed body
is accommodated in the rear of the holder 7. The third ink guiding
member 83 which guides ink to the rear face of the ball 24 and
includes an extrusion-molded body of a synthetic resin is
accommodated in the pen point 2. The rear end of the third ink
guiding, member 83 intrudes into and is connected to the leading
end of the second ink guiding member 82, while the leading end of
the first ink guiding member 81 intrudes into and is connected to
the rear end of the second ink guiding member 82. The third ink
guiding member 83 is allowed to abut on the inner surface (rear
inner surface) of each inwardly projecting portion 23.
Method for Forming Carbonaceous Film
In the writing instrument according to the present invention, the
carbonaceous film is formed on at least one of the ball or the ball
holding portion. A method of forming a carbonaceous film will be
explained below. As an example, a method of forming a carbonaceous
film on a ball surface will be explained. A similar method can also
be applied to the case of forming a carbonaceous film on a ball
holding portion.
Prior to the formation of the carbonaceous film on the ball
surface, an intermediate layer can be formed. The case of forming
an intermediate layer including an amorphous film containing Si and
C on the surface of the ball will be explained. For the film
formation of the intermediate layer, for example, an ionic vapor
deposition method can be used. In the method, the interior of a
chamber for ionized deposition is adjusted to predetermined
pressure using a vacuum pump, tetramethylsilane
(Si(CH.sub.3).sub.4) is introduced into the chamber, and a bias
voltage (for example, 1 kV) is applied to the ball to cause
discharge (for, e.g., 30 minutes). The intermediate layer can be
formed on the whole surface of the ball by rotating the ball in the
chamber when the film is formed.
After the formation of the intermediate layer, the gas supplied
into the chamber is switched to benzene to form the carbonaceous
film. The interior of the chamber is adjusted to predetermined
pressure using a vacuum pump, and a bias voltage (for example, 1
kV) is thereafter applied to the ball to cause discharge (for,
e.g., 90 minutes). The carbonaceous film can be formed on the whole
surface of the ball by rotating the ball in the chamber when the
film is formed.
Thereafter, plasma irradiation is optionally performed in an
atmosphere containing oxygen to introduce a carbon-oxygen bond into
the carbonaceous film. Plasma irradiation is performed at a
pressure adjusted to, for example, 100 Pa in the chamber and at an
output of, for example, 10 W, whereby the ball of interest can be
obtained.
The rate of the carbon-oxygen bond contained in the obtained
carbonaceous film can be evaluated by X-ray photoelectron
spectroscopy (XPS) measurement. Measurement conditions are adjusted
depending on the kind, thickness, and the like of a carbonaceous
film to be formed, for example, a detection angle with respect to a
sample can be 90.degree., Al can be used as an X-ray source, and
X-ray irradiation energy can be 100 W. Time of one measurement is
generally around 0.1 ms. Further, in order to enhance measurement
accuracy, measurement of one sample may be performed several times,
for example, 64 times to regard the average value thereof as a
measurement result.
In order to determine the rates of C--O, C.dbd.O, and O.dbd.C--O in
the carbonaceous film, a carbon 1s (C1s) peak obtained by the XPS
measurement is decomposed, by curve fitting, into seven components
of sp.sup.3 C--C and sp.sup.2 C--C in which carbon and carbon are
bound to each other, sp.sup.3 C--H and sp.sup.2 C--H in which
carbon and hydrogen are bound, and C--O, C.dbd.O, and O.dbd.C--O in
which carbon and oxygen are bound. It is appropriate for the curve
fitting to allow the bond energy of sp.sup.3 C--C to be 283.8 eV,
the bond energy of sp.sup.2 C--C to be 284.3 eV, the bond energy of
sp.sup.3 C--H to be 284.8 eV, the bond energy of sp.sup.2 C--H to
be 285.3 eV, the bond energy of C--O to be 285.9 eV, the bond
energy of C.dbd.O to be 287.3 eV, and the bond energy of O.dbd.C--O
to be 288.8 eV. A value obtained by dividing the area of each peak
obtained by the curve fitting by the overall area of the C1s peak
is regarded as the composition ratio of each component. The sum of
the composition ratios of C--O, C.dbd.O, and O.dbd.C--O is regarded
as the rate (CO.sub.total) of carbon-oxygen-bound carbon atoms to
the total carbon atoms.
The thicknesses of the intermediate layer and the carbonaceous film
can be measured by analyzing the ball, on which the carbonaceous
film is formed, with an Auger electron spectroscopy device (PHI-660
Type (trade name), manufactured by ULVAC-PHI, Inc.). Specifically,
the surface of the ball on which the carbonaceous film is formed is
etched in stages, and the surface is analyzed at each stage by an
Auger electron spectroscopy analysis method. As measurement
conditions, for example, the acceleration voltage of an electron
gun is set at 10 kV, a sample current is set at 500 nm, and the
acceleration voltage of an argon ion gun is set at 2 kV. A region
measuring 40 .mu.m per side on the ball surface is analyzed at each
depth under the measurement conditions, whereby the thicknesses of
the intermediate layer and the carbonaceous film can be
measured.
When a ball with a carbonaceous film produced by the method was
analyzed, the following results were obtained. In the depth from
the surface of the ball, on which the carbonaceous film was formed,
to around 80 nm, only carbon atoms (C) substantially existed, and
the carbonaceous film was formed. In the depth of 80 nm to 120 nm,
Si atoms existed, and an intermediate layer comprising SiC was
formed. In the portion having a depth of 100 nm or more, only
tungsten carbide (WC) was detected, and the intermediate layer and
the carbonaceous film were confirmed to be formed on the surface of
the tungsten carbide which was the ball.
EXAMPLE
A ball (DLC-1) on the ball surface of which a carbonaceous film was
formed and a ball (DLC-2) in which a carbonaceous film in which the
rate of carbon-oxygen bond was varied by changing plasma
irradiation conditions was obtained were produced by the method.
Specifically, DLC-1 was irradiated with oxygen plasma for 60
seconds at an output of 10 W from a high frequency power source.
DLC-2 was irradiated with oxygen plasma for 60 seconds at an output
of 50 W from the high frequency power source. The rate of each bond
contained in the carbonaceous films formed on the balls was
measured by the method. The obtained results are as listed in Table
1.
TABLE-US-00001 TABLE 1 sp.sup.3C--C C--C + C--H C--O C.dbd.O
O.dbd.C--O CO.sub.total sp.sup.2C--C DLC-1 0.84 0.13 0.02 0.01 0.16
0.39 DLC-2 0.57 0.21 0.13 0.09 0.43 0.42
The proportions (CO.sub.total) of carbon atoms bound to oxygen
atoms with respect to the total carbon atoms in DLC-1 and DLC-2
were 0.16 and 0.43, respectively. The value of CO.sub.total in
DLC-2 with the higher power output in the irradiation with oxygen
plasma was higher than that in DLC-1. CO.sub.total is further
detailed as follows: the proportions of C--O to the total carbon in
DLC-1 and DLC-2 were similar, while the proportion of C.dbd.O in
DLC-2 was about 6 times that in DLC-1, and the proportion of
O.dbd.C--O in DLC-2 was about 9 times that in DLC-1. Further, the
proportions of sp.sup.3 carbon-carbon bonds to sp.sup.2
carbon-carbon bonds in the carbonaceous films were 0.3 or more.
Then, a contact angle between the surface of each ball of a
tungsten carbide ball (WC) on which no carbonaceous film was
formed, DLC-1 described above, or DLC-2 described above, and an ink
for a writing instrument was measured. The measurement was
performed using, as an ink for a writing instrument, a blue ink
comprising 5.0 mass % of a blue dye (WATER BLUE 105S (trade name),
manufactured by ORIENT CHEMICAL INDUSTRIES CO., LTD.), 0.5 mass %
of a lubricating interface layer-forming compound (phosphate ester
(PLYSURF AL (trade name), manufactured by DKS Co. Ltd.)), 1.0 mass
% of triethanolamine, 5.0 mass % of diethylene glycol, 3.0 mass %
of 2-pyrrolidone, and 85.5 mass % of water. When the viscosity of
the ink was measured using a B type viscometer ((BL ADAPTOR)
manufactured by TOKYO KEIKI INC.), the viscosity of the ink was 2
mPas under an environment of 20.degree. C. In addition, the pH
thereof was 9.0.
As for a contact angle between the surface of each ball and the ink
for a writing instrument, in comparison with the contact angle of
the untreated WC ball, the contact angle of DLC-1 is less, the
contact angle of DLC-2 is further less, and the affinities thereof
are high. It is clear that an affinity for an ink for a writing
instrument is improved by forming a carbonaceous film having a
carbon-oxygen bond.
For the measurement of a contact angle, an automatic contact angle
measuring machine (DM-500 (trade name) manufactured by Kyowa
Interface Science Co., Ltd.) was used. Dropwise addition of 1 .mu.l
of the water-based ink onto the surface of a test plate (WC,
equivalent to ISO K-10) having a carbonaceous film disposed under
the same conditions as those of the carbonaceous film disposed on
the ball was performed to measure a contact angle. The timing of
the measurement was just after the dropwise addition, and the
measured value was an average value at three points. In the case of
an ink having a comparatively high viscosity, for example, in the
case of a water-based gel ink or an oil-based ink, the contact
angle can be determined by measurement performed 3 seconds after
the dropwise addition (measured value was an average value at three
points).
The surface tension of the water-based ink was 40 mN/m. The surface
tension of an ink is preferably 20 mN/m or more and 40 mN/m or
less, most preferably 25 mN/m to 35 mN/m, under an environment at
20.degree. C. so that the ink is smoothly supplied when an ink tank
is exchanged. As a method for measuring the surface tension, the
surface tension can be determined by measurement by a vertical
plate method using a glass plate, under an environment at
20.degree. C., using a surface tension measuring instrument
manufactured by Kyowa Interface Science Co., Ltd.
Then, a writing implement including each ball described above was
prepared to conduct a running test. The test is a test in which a
writing instrument is retained in the state of being tilted at
70.degree. with respect to a paper surface and is rotated to draw a
circle having a diameter of 32 mm at a load of 100 gf (about 0.98
N), and a writing distance by the writing instrument is
investigated using a tester that moves writing paper (JIS: P3201)
at a speed of 4 m/min. Writing of a distance of about 10 cm is
achieved by drawing one circle by the writing instrument. A
distance from the leading end of a pen point to the leading end
position of the ball was measured every 100 m of the writing
distance. Since the distance from the leading end of the pen point
to the leading end position of the ball was shortened due to wear
of the ball and the ball holding portion, the change amount
(depression amount) of the leading end position of the ball was
regarded as a wear amount. Further, after the exhaustion of the ink
filled in the ink tank, the ink tank was exchanged, and the running
test was further continued.
As a result of measuring the wear amount mentioned above, the
result of untreated ball (WC) on which no carbonaceous film was
formed>carbonaceous film (DLC-0) into which no carbon-oxygen
bond was introduced>DLC-1>DLC-2 was obtained. This is
considered to be because, when the carbonaceous film having a
carbon-oxygen bond was formed, an affinity between the ball and the
water-based ink was improved, direct contact between the ball and
the ball holding portion hardly occurs, and therefore, the ball and
the ball holding portion were inhibited from being worn, although
boundary lubrication is considered to occur between the ball and
the ball holding portion in the water-based ink. Further, DLC-0
resulted in a large wear amount and in nonuniform handwriting in
the writing of 2000 m. In contrast, in DLC-1 and DLC-2, stable
writing performance was able to be maintained even in the writing
of 3000 m and 5000 m.
The specific change amount (depression amount) of the leading end
position of the ball in DLC-1 was 0 .mu.m in non-writing, 3 .mu.m
after 0-100 m writing, 4 .mu.m after 500 m writing, or 4 .mu.m
after 1000 m writing. As a result of further exchanging a cartridge
and performing continuous measurement, the amount was 5 .mu.m after
1500 m writing, 5 .mu.m after 2000 m writing, 6 .mu.m after 3000 m
writing, or 6 .mu.m after 5000 m writing. Depending on the
composition and viscosity of an ink, uniform handwriting is
inhibited when the change amount (depression amount) of the leading
end position of the ball is more than 10 .mu.m.
In DLC-1, a wear amount of 3 .mu.m after 0-100 m writing is
slightly large; however, since this is because the ball and the
ball holding portion conform to each other to form an abutting
surface from a writing distance of 0 m to a writing distance of 100
m, and then, wear does not occur or only slight wear occurs due to
the carbonaceous film, stable writing performance is satisfied for
a long period.
As a result of measuring a wear amount by the method mentioned
above using, as the water-based ink for a writing instrument, a
water-based ink (pH 9.0) comprising 40.0 mass % of a water soluble
dye (WATER BLACK 191L (trade name), manufactured by ORIENT CHEMICAL
INDUSTRIES CO., LTD.), 1.0 mass % of sarcosine (lubricating
interface layer-forming compound), 1.0 mass % of triethanolamine
(pH adjuster), 5.0 mass % of ethylene glycol, and 53.0 mass % of
water, the result of untreated ball (WC) on which no carbonaceous
film was formed>carbonaceous film (DLC-0) into which no
carbon-oxygen bond was introduced>DLC-1>DLC-2 was
obtained.
As a result of conducting a running test at a load of 400 gf by the
method mentioned above using, as the oil-based ink for a writing
instrument, an oil-based ink comprising 20.0 mass % of a dye
(SPILON BLACK GMH-SPECIAL (trade name), manufactured by Hodogaya
Chemical Co., Ltd.), 18.0 mass % of a dye (VALIFAST VIOLET 1701
(trade name), manufactured by ORIENT CHEMICAL INDUSTRIES CO.,
LTD.), 23.0 mass % of benzyl alcohol, 32.0 mass % of ethylene
glycol monophenyl ether, 2.0 mass % of oleic acid (lubricating
interface layer-forming compound), 2.0 mass % of NYMEEN L-201
(trade name, manufactured by NOF CORPORATION), 0.5 mass % of
polyvinyl pyrrolidone (agent for imparting stringiness), and 2.5
mass % of a viscosity modifier (HILACK 110H (trade name),
manufactured by Hitachi Chemical Company, Ltd.), to measure a wear
amount, the result of untreated ball (WC) on which no carbonaceous
film was formed>carbonaceous film (DLC-0) into which no
carbon-oxygen bond was introduced>DLC-1>DLC-2 was obtained.
When the viscosity of the ink was measured using a B type
viscometer (manufactured by TOKYO KEIKI INC.), the viscosity of the
ink was 1500 mPas under an environment of 20.degree. C.
As a result of conducting a running test at a load of 400 gf by the
method mentioned above using the oil-based ink, to measure a wear
amount, the result of untreated ball (WC) on which no carbonaceous
film was formed>carbonaceous film (DLC-0) into which no
carbon-oxygen bond was introduced>DLC-1>DLC-2 was
obtained.
REFERENCE SIGNS LIST
1 Writing instrument
2 Pen point
21 Pipe
22 Leading edge
23 Inwardly projecting portion
24 Ball
24A Ball body
24B Intermediate layer
24C Carbonaceous film
3 Ink reservoir member
31 Comb
32 Reservation groove
33 Guiding groove
34 Collar portion
35 Communication groove
36 Concave groove
37 Central hole
4 Ink tank
41 Plug body
5 Leading shaft
51 Threaded engagement portion
51a Male screw portion
52 Binding portion
52a Projection
6 Rear shaft
61 Female screw portion
7 Holder
8 ink guiding member
81 First ink guiding member
82 Second ink guiding member
83 Third ink guiding member
* * * * *